Scientists are making strides in growing food in space, and their efforts could be critical to eventually supporting a permanent human colony on Mars.

“We can grow plants on Mars just by compressing the atmosphere,” SpaceX founder and CEO Elon Musk said Tuesday in a long-awaited speech detailing his vision for sending humans to Mars by 2025. The billionaire engineer said the Red Planet is “resource rich” with water ice and compounds necessary to support plants, such as nitrogen.

Experts say astronauts could pack enough packaged or freeze-dried food to get to Mars and back, although living on the planet for extended periods would get increasingly difficult without regular food-supply missions. Mars would require a six-month journey to the planet, an 18-month stay and a six-month trip back.